Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations, so the description carries the full burden. It usefully discloses the 100-item cap, auto-detection behavior, and result ordering with a summary count, but says nothing about side effects, auth/permissions, rate limits, or whether DNS lookups (check_dns default true) cause network calls.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight, front-loaded sentences with no filler; the batch constraint leads and the output format follows. The phrase 'per agent_action' is unexplained jargon that slightly muddies the second sentence.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 3-parameter tool with no annotations and no output schema, the description is only partially sufficient. Ordering and summary output are covered, but the two optional parameters and any safety/network behavior remain undocumented.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must document parameters. It only covers 'values' (contents plus the 100 max), and completely omits check_dns and default_country, leaving two of three parameters with no semantic explanation anywhere.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (validate emails/phone numbers), plus batch scope of up to 100 with auto-detected type. This distinguishes it implicitly from validate_email and validate_phone, but it never names those siblings, so an agent must infer the batch-vs-single split.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The 'up to 100 ... at once' and 'type is auto-detected' phrasing implies the mixed/bulk use case versus the single-type siblings, but there is no explicit when-to-use, when-not-to-use, or named alternative guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.